Penta-EF-hand domain containing 1 (PEF1) is a member of the penta-EF-hand protein family, which shares similarities to the apoptosis linked gene ALG-2. PEF1 forms heterodimers with PDCD6/ALG2 and dissociates from PDCD6/ALG2 in the presence of Ca (2+). Furthermore, PEF1 proteins bind calcium and participate in a various calcium-dependent processes in vertebrates.